I know it's available on Ipad as well though I use it on my Android tablet and phone but I can recommend Google docs. It's got a good spell check, better then word sometime, and it can be used online or via the app. You can use it for word processing and spreadsheets, though I have to admit I've never used the spreadsheet function, but I hear it's good.

I reccommend Documents. It's never crashed and is extremely reliable and easy to use - I've written novel-length pieces on it, it couldn't be easier to use. I use the free version which has everything I need but there's also a paid version if there's extra features you want.